Use of lepidolite as an additive in the lime-roasting of lithium-aluminosilicate ores



United States Patent USE or LEPIDOLITEAAS ADDITIVE IN THE Ln/rE-noAsrrNG or LITI-IIUM-ALUMINOSILI- earn onus Harold Mazza, Stanley L. Cohen, and Glen H. S chafer,

Trona, Califi, assignors to American Potash & Chemical Corporation, a corporation of Delaware N 0 Drawing. Application August 18, 1955,

Scrial'No. 529,348 r 4 Claims. Il. 75-1) This invention relates to recovery of lithium from the lithium-containing ores, spodum'ene andpetalite. It is known that these lithium ores can be roasted with calcium carbonate to render the lithium content water soluble, the soluble lithium salts being, thereafter, extracted. In effecting the roasting of these ores, it is necessary to use relatively high temperatures, e. g'., temperatures of the order of 1100 and 1200 C.

We have found that these lithium ores can be successfully roasted with calcium carbonate, at a significantly lower temperature and to economic advantageif lepidolite is present as a constituent in the roast. "Apparently, the fluxing constitutents in the lepidolite are such that they enable the lithium values to be extracted from such ores when these are first roasted with calcium carbonate at temperatures of the order of 800 to 950 C. It has heretofore been necessary to heat spodumene and petalite to temperatures of the order of 1000-1200 C. to change their mineral form to one upon which subsequently limeroasting could be successfully practiced. Thus, the presence of lepidolite in the roast obviates the heating to a high temperature of spodumene or petalite and enables the lime-roast to be carried out at a much lower temperature.

Typical analyses of lepidolite and of the lithium TABLE II Test N o.

I II III IV Lepidolite, grams 12. 96 12. 96 14. 28 14. 28 Petallte, grams 19. 44 19.44 Spodumene, grams... 21. 42 21. 42 Limestone, grams 117. 6 117. 6 114. 3 114. 3 Limestone-ore ratio. 3. 63:1 3. 63:1 3. 2: 1 3. 2:1 Roast; temperature, 900 900 900 900 Roast time, hours 1. 75 2 2 2. 25 CO2 content of clinker, percent 6. 8 6. 5 5. 6 5. 0' Lithium recovery, percent 78. 7 82. 5 84. 4 85. 0 Alumina in leach liquor, percent 0. 004 0. 004 0. 004 0. 004

as before. The results are tabulated below:

TABLE III Test No.

I II III IV Lepidolite, grams 12. 9e 12. so 14. 2s 14. 2s Peta'lite, grams 19. 44 19. 4'4 Spodumene, grams 21. 42 21. 42 Limestone, grams 117. 6 117. 0 114. 3 114. 3 Limestone-ore ratio. 3. 63:1 3. 63:1 32:1 3.2: 1 Roast temperature, 1, 200 1, 200 1, 100 1, 100 Roast time, hours 2 2 2 2 002' content of clinker, percent 0.80 0. 75 O. 58 0. 53 Lithium recovery, percent 46. 8 50. 9 63. 7 50. 9 Lithium lost through vaporization,

percent 35. 7 32.3 7. 7 15.2 Alumina in leach liquor, percent-. 0. 004 0. 004 0. 004 0. 004

The lithium recovery is based on the quantity of lithium aluminosilicate ores are given in Table I. hydroxide recovered in the leach liquor. The recovery TABLE I Ore LizO, NaaO, K20, RbzO, CszO, SiOz, A1101, F,

Percent Percent Percent Percent Percent Percent Percent Percent 4.19 0. 56 8.55 3.39 0. 25 52.3 28.8 5.88 6.00 0.55 0.48 none none 63.6 28.7 none 4. 73 0.17 0.02 none none 777 17.1 none The practice of the present invention will become furwas low because lithium values were volatilized during ther apparent upon consideration of the following. roasting and hence were lost to the leach system. The E l A series f roasts were d using (1) data shown in Tables II and III show that the use of mixtures f 0% Petalite and 40% lepidolite and 2 lepidolite as an additive to either petalite or spodumene mixtures of 60% spodumene and lepidolite. The permits the ores to be roasted at temperatures substanlimestone-to-ore ratio on a Weight basis was 3.63 to 1 for tilany lower than Wquld necessary if these ores the petalite-lepidolite mixtures, and 3.2 to 1 for the spodhmefoasted alone; s 900 C. rather than 1100 to umene-lepidolite mixtures; these ratios were such as to 9 maintain a constant calcium-to-silica ratio in the charge. f 9 roasts F using The individual charges consisted, respectively, of 12.98 3 petalte 10% i mlxtures grams of lepidolite and 19.44 grams of petalite with 117.6 E Spo and lepldo AS m Example rams limestone and 14.28 rams of le idolite and 21 42 l-lmestgneto-ore who was to 1 for the Imam:- g f d 1143p lepidolite mixtures, and 3.2 to 1 for the spodumenegfg SP0 umene mlxed 1 l l lepidolite mixtures. The individual charges consisted reese c arges were roaste 1n stain ess stee crucibles 1n specfively of 324 grams of lepidolite and 2916 grams a laboratory muffle funface at 900 for from to of petalite mixed with 117.6 grams of limestone, and 150 m1nu tes, as Sh WH 1 tho fOHOWIIIg tables; 1116 357 grams of lepidolite and 32.14 grams of spodumene Sultlng Chnkers were h q l 111 one liter of hot mixed with 114.3 grams limestone. The methods of Water and then leached with agltatlon and at boiling under roasting and leaching the charges were identical to those reflux for sixteen hours. The results obtained are tabugiven in Example 1. The results obtained are tabulated lated below: below:

For comparative purposes, the results obtained when lime-roasting petalite and spodumene at the temperatures and for the roast times used in Examples 1 and 2 are shown below:

TABLE V Test N 0.

I II III IV Petalite, grams 50 50 Spodumene, grams 50 50 Calcium carbonate, gram 150 150 150 150 Calcium carbonate-ore r- 3. 01:1 3. 1 3. 0:1 3. 0:1 Roast temperature, C 900 1200 000 1100 Roast time, hours"... 2 2 Lithium recovery, percent. 10 9 S1. 0 13. 82. 3

A comparison of Tables IV and V shows that a marked improvement in lithium recovery can be obtained when lime-roasting petalite or spodumene at 900 C. by adding a small quantity of lepidolite to the roast mixture. As can beseen from the data, the quantity of lepidolite can be as low as approximately 10% of the weight of the total lithium ore treated. The lepidolite content of the charge can be increased until lepidolite provides substantially the only lithium source, but, as we have indicated, the temperature of the roast can be reduced to 900 C. when as little as 10% is present. The utilization of a larger quantity of lepidolite, e. g., about 40%, makes it possible to provide a very economical process for the recovery of lithium values at relatively low roast temperatures.

Spodumene and petalite mixtures can also be roasted successfully by adding lepidolite to such a mixture. The limestone to mixed ore ratio must be based on the effective or available quantity of calcium carbonate present. Thus, one should correct the actual quantity of limestone by taking into account the quantities present of magnesium oxide, silica, and alumina. Magnesium carbonate is effective as a substitute for calcium carbonate to a limited extent. Those skilled in the ore roasting art will have no difiiculty in selecting a good limestone and in arriving at the proper quantity of the natural limestone selected. I

We claim:

1. In a lime-roast process for recovering lithium, the step comprising roasting a finely divided mixture of calcium carbonate, lepidolite and an ore selected from the group consisting of spodumene, petalite, and mixtures thereof, at a temperature of from about 800 C. to about 950 C., the lepidolite providing at least approximately 10% of the total weight of the lithium ore mixture.

2. In a lime-roast process for recovering lithium, the step comprising roasting a finely divided mixture of calcium carbonate, lepidolite and an ore selected from the group consisting of spodumene, petalite, and mixtures thereof, at a temperature of from about 800 C. to about 950 C., the lepidolite providing at least approximately 40% of the total weight of the lithium ore mixture.

3. In a lime-roast process for recovering lithium, the step comprising roasting a finely divided mixture of calcium carbonate, lepidolite and an ore selected from the lithium-aluminosilicate group such as spodumene and petalite, and mixtures thereof, at a temperature of from about 800 C. to about 950 C., the lepidolite providing at least approximately 10% of the total weight of the lithium ore mixture, the available calcium carbonate to lepidolite and ore ratio being between three and four to one.

4. In a lime-roast process for recovering lithium, the step comprising roasting a finely divided mixture of calcium carbonate, lepidolite and an ore selected from the lithium-aluminosilicate group such as spodumene and petalite, and mixtures thereof, at a temperature of from about 800 C. to about 950 C., the lepidolite providing at least approximately 40% of the total weight of the lithium ore mixture, the available calcium carbonate to lepidolite and ore ratio being between three and four to one.

Rosett Nov. 12, 1935 Kroll Dec. 15, 1953 

1. IN A LIME-ROAST PROCESS FOR RECOVERING LITHIUM, THE STEP COMPRISING ROASTING A FINELY DIVIDED MIXTURE OF CALCIUM CARBONATE, LEPIDOLITE AND AN ORE SELECTED FROM THE GROUP CONSISTING OF SPODUMENE, PETALITE AND MIXTURES THEREOF, AT A TEMPERATURE OF FROM ABOUT 800* C. TO ABOUT 950* C., THELEPIDOLITE PROVIDING AT LEAST APPROXIMATELY 10% OF THE TOTAL WEIGHT OF THE LITHIUM ORE MIXTURE. 